But, he pointed out, it was still a strong indicator that a relatively brief intervention could have a positive effect in preventing zero-gravity muscle loss -- one that might also be applied on Earth.

By IANS, [RxPG] When the Apollo 11 crew got back from the moon some 40 years ago, they showed no ill effects from a week spent in weightlessness. But as space men began conducting longer-duration space flights, scientists noticed a disturbing trend: the longer humans stay in zero gravity, the more muscle they lose.

Space travellers exposed to weightlessness for a year or more -- such as those on a mission to Mars, for example -- could wind up crippled on their return to Earth, unable to walk or even sit up.

Now, researchers at the University of Texas Medical Branch-Galveston - have conducted the first human experiments using a device intended to counteract this effect.

It is a NASA centrifuge that spins a test subject with his or her feet outward 30 times a minute, creating an effect similar to standing against a force two and half times that of gravity.

Working with volunteers kept in bed for three weeks to simulate zero-gravity conditions, they found that just one hour a day on the centrifuge was sufficient to restore muscle synthesis.

'This gives us a potential countermeasure that we might be able to use on extended space flights and solve a lot of the problems with muscle wasting,' said Douglas Paddon-Jones, senior study co-author.

'This small amount of loading, one hour a day of essentially standing up, maintained the potential for muscle growth,' he added.

Fifteen healthy male volunteers participated in the study.

The results showed that members of the centrifuge group continued to make thigh muscle protein at a normal rate, while the control group's muscle synthesis rate dropped by almost half.

Paddon-Jones cautioned that the rate of muscle protein synthesis alone does not necessarily predict changes in muscle function.

But, he pointed out, it was still a strong indicator that a relatively brief intervention could have a positive effect in preventing zero-gravity muscle loss -- one that might also be applied on Earth.

These findings were published in the July issue of the Journal of Applied Physiology.